DALLAS (CBSDFW.COM/AP) — A federal grand jury has indicted a Dallas-area man in the killing of a postal worker who was driving a delivery rig on a Dallas expressway.

A statement by the U.S. Attorney’s Office in Dallas said 25-year-old Donnie Arlondo Ferrell of Hutchins is charged with murder of a U.S. officer or employee and a firearms violation.

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Donnie Ferrell (Dallas County Jail)

The indictment also charges 24-year-old Bei-jing Tashawna Walker, aka “Channelle Walker” of Hutchins, with aiding and abetting Ferrell after the Feb. 19 shooting by helping him avoid arrest.

Both will remain jailed pending trial.

Investigators say 58-year-old Tony Mosby was driving the rig, known as a box truck, when he was shot. He was found dead in the truck, which had crashed into a guardrail on Interstate 30 near downtown Dallas.

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Tony Mosby (Facebook)

According to the arrest affidavit, the motive for the murder was apparently road rage. Ferrell was allegedly drinking with friends and was angered by a hand gesture from Mosby while passing him on the freeway.

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)